Temperature-dependent biquadratic coupling in antiferromagnetically coupled Fe/FeSi multilayers

Fe/FeSi multilayers are known to exhibit a strong antiferromagnetic interlayer coupling peak centered at a nominal FeSi spacer thickness of similar to 15+/-2 Angstrom at room temperature, and to develop remanence in the magnetic hysteresis loop upon cooling to similar to 100 K. An analysis of the hysteresis loops is found to require the inclusion of a temperature-dependent biquadratic (90 degrees coupling) in addition to the bilinear coupling term in the energetics. The temperature dependence of the Fe/FeSi multilayer coupling can then be understood in terms that are applicable to conventional metallic multilayer systems such as Fe/Cr.